Cytogenetical Studies in a West African Solanum melongena L. hybrid (S. melongena var. Giwa-2×var. Giwa-1)

Abstract

The haploid and diploid number of chromosomes in S. melongena var. Giwa-2×var. Giwa-1 is found to be 12 and 24, respectively. The chromosomes exhibit differences in size and their morphology, having metacentric and submetacentric centromeres.
In meiosis pairing begins at a point near the centromere and generally passes along the length of the chromosomes. Where three of four homologous segments of chromosomes lie together, pairing appeared in two of the three or four chromosome threads in a particular segments. Pairing is allosyndetic, 12 chromosomes of Giwa-2 pairing with 12 chromosomes of Giwa-1.
Frequencies of chiasmata at diplotene and diakinesis are analysed. The frequency per bivalent at diplotene and diakinesis varied from 1.91 to 1.28, respectively.
Multivalent chromosomes in form of quarivalents and trivalents occurred in 31.9 % cases observed. The occurrence of high frequency of multivalents in a diploid hybrid seemed to indicate the presence of translocation interchanges in S. melongena var. Giwa-2×var. Giwa-1.
The univalents occurred in 29.8 % cases observed. Structural changes are probably responsible for failure of pairing among pairable chromosomes. The behaviour of univalents varied, they either pass to the poles or lag (18.4%) or eliminated (11.4%). The elimination of univalents causes unequal distribution of chromosomes on second metaphase plates. Univalents and fragments failed to be included in the daughter nuclei formed micronuclei.
The high frequency of pairing of chromosomes in the hybrid indicates that two varieties of S. melongena, Giwa-1 and Giwa-2 are closely related.